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| Identification of Allopolyploids of Chinese Cabbage (Brassica campestris L.ssp. pekinensis(Lour.) Olsson) and Cabbage (B. oleracea var. capitata L.) |
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Abstract Allopolyploid can be used as a bridge to overcome distant hybridization barriers and a promising approach to improve varieties. In this study, allotriploid and allotetraploid hybrids between Chinese cabbage(Brassica campestris L.ssp.pekinensis(Lour.) Olsson) and cabbage (B. oleracea var. capitata L.) were identified by morphological, anatomical and cytological observation and molecular markers analysis. Results showed that polyploidy plants showed obvious heterosis in plant types, floral organ and stomata sizes and allotetraploid heterosis was more obvious than that of allotriploid generally. The pollen viability and stomata density of polyploids were lower than that of both parents and pollen viability of allotriploid was the lowest of 18.78%, whereas it reached 81.56% in allotetraploid. The seed setting rates in the selfing of allopolyploids were lower than that of both parents, which in selfing of allotetraploid was 0.28%. The seeds setting rate was higher in crossing allotetraploid with Chinese cabbage than that in their inverse cross combinations, which increased by 2.11 times. The seed setting rate of reciprocal crosses between allotriploid and Chinese cabbage was very low, and no seed was obtained in the selfing of allotriploid. The SRAP assay further confirmed that polyploids included the genetic information of their parents and were the true hybrid, while it was hard to distinguish allotriploid from allotetraploid by SRAP. Cytological identification revealed that the allotetraploid had putative chromosomes (2n=4x=38) and the allotriploid had putative chromosom(2n=3x=29). The obtaining and identification of allopolyploids provide a foundation for the improvement of Chinese cabbage cultivars in the near future.
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Received: 14 March 2012
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